The present invention generally relates to apparatus and method for insulation in plasma discharge systems. Specifically, the invention pertains to a structure and method in which a conductive confinement is implemented to contain a plasma discharge at optimal fill volume and with the least insulation breakdown. More specifically, the invention provides a method of applying an anodized insulation layer on the surface of the conductive confinement to prevent shorting of and interference with the plasma discharge formed and maintained between a pair of widely separated anode and cathode terminals. A plurality of bias resistors are implemented, to provide optimization of the potentials between the conductive confinement and the anode, in order to promote best plasma fill with a substantially reduced risk of insulation breakdown.
Generally, plasma is defined as a mixture composed of neutral particles, ions and electrons. In a plasma mass there is no net space charge and the composition of a plasma mass is a function of temperature and pressure. Specifically, as the temperature of a plasma mass is increased the electrical conductivity increases also.
Plasma generation is well-known in the art. Conventional plasma generation systems utilize an anode and cathode terminals with spatial separation therebetween. A power source supplies electrical energy to the terminals and generally a sacrificial fuse is evaporated/consumed to generate highly ionized plasma between the terminals.
The prior art method for producing plasma inside a container is to drive electric current between a pair of electrodes mounted in the container. The interior is preferably filled with helium, equivalent gas or mixture of gases maintained at below the atmospheric pressure. To maintain the flow of electric current through the contained gas, there must be a potential difference (voltage) between the discharge electrodes. This voltage is typically maintained by a high-voltage power supply or radio frequency (RF) power supply. If the container is made of a dielectric substance such as glass or insulation material, the required voltage difference is easily maintained even if the discharge electrodes are widely separated. However, for some applications, dielectric substances such as glass are unsuited for plasma containment because of breakage, cost or other mechanical and fabrication problems. For these applications, metallic containers are best suited. However, metallic containers because of their conductivity tend to interfere with the formation and fill-volume of plasma contained therein.
Specifically, while generating plasma does not pose significant technical difficulties, the containment of plasma in metallic vessels requires highly specialized equipment. More specifically, plasma appears to have unpredictable hydrodynamic and electrical properties when placed in metallic containers.
Accordingly, it would be preferable to use metallic vessels provided direct contact between the stored plasma and the metallic walls of the container is avoided.
The present invention provides a device and method for containing a plasma discharge in a substantially conductive container. Specifically, the invention discloses a structure and method to optimally fill the container with plasma discharge without the associated problems of electrical shorting of the plasma by the conductive container.
It is the object of the present invention to provide a structure to contain plasma discharge within a container at best fill capacity of the container and minimum dielectric breakdown. In significant parts, the invention includes a plasma discharge containment chamber in a structure having an inner and outer surfaces. Specifically, cathode and anode terminals are interstitially disposed and supported at the inner surface of the containment chamber. Further, a dielectric layer forms an epidermic cover on the inner surface. A power source is also connected to the anode and cathode terminals to provide a plasma discharge source. Further, ballast type resistors are connected to the power source. The resistors are connected to the outer surface of the container and the anode terminal. These connections generally provide the basic architecture for operable electrical connections to the cathode terminal via the power source to confine the plasma discharge at optimal space-volume capacity of the containment chamber.
It is another object of the invention to provide a device to optimize container and anode potentials for best plasma fill of the container while attenuating insulation breakdown. Significant elements of the structure include the container forming an enclosed structure; an anode and a cathode terminals attached to internal surfaces of the container; a power source connected to the cathode terminal and a first and second bias resistors connected to the power source. The internal surfaces are generally formed from an anodized layer applied to the container and the first bias resistor is preferably connected between a positive terminal of the power source and the container. Further, the second bias resistor is connected between the positive terminal of the power source and the anode terminal.
It is yet another object of the invention to provide a method for electrical insulation in plasma discharge containers, to maintain the plasma discharge at best fill capacity of the container and minimum dielectric breakdown. In general, the method includes providing a plasma discharge containment chamber having an inner and outer surfaces; coating the inner surface to form an anodized layer therein; placing a cathode and anode terminals in a spaced-apart relations therewith on the inner surface of the container; providing a power source with a negative and positive terminals having operable electrical connections with the cathode terminal on the negative side and with a plurality of bias resistors on the positive side. Further, the preferred method includes the further steps of connecting one of the plurality of bias resistors to the outer surface of the container; connecting another one of the plurality of bias resistors to the anode terminal and controlling voltage across the inner and outer surfaces by choosing appropriate values for the plurality of bias resistors.